The present invention relates to a check valve which is capable of checking low reverse flows and, more particularly, to a check valve comprised of a membrane which is thin enough to react to low flows and which is made of a material which is not materially affected by static charge.
Check valves have long been known in the prior art. These check valves, which are analogous to a diode in an electronic setting, are used to allow fluid flow in only one direction. Thus, any reversal of the fluid flow in the undesired direction results in stoppage or checking of the flow.
Typical prior art check valves which use a disc which opens for flow in a first direction but which closes up against the housing for flow in the reverse direction have not been able to respond to low flows and pressure differentials in either direction. In the forward direction, they require a large flow and/or pressure differential in order to produce a useful output. When air flow reverses, prior art check valves will not close off until a larger than necessary pressure differential is attained. Until closed off, therefore, reverse flow will be permitted. Thus, many of these prior art check valves require nearly an inch of water pressure or more across the disc in the reverse direction for checking flow. The present invention, however, requires as little as 0.001 inches of water differential pressure across the membrane in order to check flow in the reverse direction.